From: "Stephan Kämper" <Stephan.Kaemper@...>
Date: 2002-02-25T21:44:00+09:00
Subject: Re: inconsistence in class complex

GOTO Kentaro wrote:
> 
> > As far as I see, Complex inherits from Numeric and that's OK.
> > And it doesn't include Comparable, which relects the fact that complex
> > numbers can'T be compared with '>' and the like.
> 
> I agree halfly.
> 
> In Ruby world, Module forms partialy order, i.e., A < B and B < C
> implies A < C for any module A,B,C.  Now, we have Complex < Numeric
> and Numeric < Comparable, therefore Complex < Comparable automatically
> even if Complex#<=> would be undefined.

Ooops, you're right. I didn't go deep enough into the the documentation.

> There are other Ruby-definable strange numeric sets, e.g., Hamilton's
> Quotanion, which has four imaginary units.  So, Complex isn't only
> special.
> 
> However, undef Complex#<=> and ignoring the fact Complex < Comparable
> seems a practical and acceptable option, IMHO.

Could be a way to go...

> To go rigorous,
> Numeric must not include Comparable but Integer, Float and Rational
> must include severally.

Yes.

Happy rubying!

Stephan